The Germ Theory of Disease

The Germ Theory of Disease states that many illnesses are caused by tiny microorganisms called germs—such as bacteria, viruses, fungi, and parasites—that invade the body. These germs can multiply and damage tissues, leading to symptoms of disease. Understanding this theory has helped develop practices like sterilization, vaccines, and antibiotics, which prevent and treat infections. Essentially, it shifted the view from miasma or bad air as causes of disease to recognizing that microorganisms are often the true culprits behind illness, improving medical care and public health.